What's the best modern battery for my Duster?

My repro battery is losing its cranking power. The new ones are around $350 plus shipping. I was thinking I could keep using the old one until it fails completely, but have a modern battery in the mean time so I don't get stranded somewhere.
Gotcha!

I used to manage the NAPA down in Savage, on Hwy 13, but that was over 25 years ago, so I don't know anyone there anymore. I do, however, still have an "in" at the NAPA up here in Osseo, if that would help you...